Attachment Component, Navigation System and Method for Tracking a Surgical Instrument

ABSTRACT

An attachment component for attaching a tracker of a surgical navigation system to a surgical instrument is disclosed. The attachment component comprises a body and an instrument interface attached to the body and configured for detachable attachment of the attachment component in a predefined position and orientation to a surgical instrument or implant. A tracker interface is attached to the body and has a fixed pre-defined shape for engagement with the tracker interface of the tracker. The instrument interface is arranged in an un-calibrated position relative the tracker interface. A navigation system comprises a tracker with a tracker interface for attachment to the attachment component. The tracker is configured to report position and orientation of its tracker interface. A method implements translation of position and orientation of the tracker into position and orientation of an instrument.

FIELD OF THE INVENTION

This invention pertains in general to the field of navigation systemsfor tracking objects in an area of interest, such as instruments. Moreparticularly, the invention can be implemented into a surgicalnavigation system for tracking position and orientation of surgicalinstruments, including implants, relative position and orientation ofpatient anatomy during surgery. The position and orientation data of theinstrument may be presented in real-time in relation to a pre-operativeplan including a virtual representation of the patient anatomy. Thenavigation system comprises a plurality of trackers. A tracker isattached to the instrument using an uncalibrated attachment componentwith an arbitrary shape unknown to the navigation system. Each of thetracker and the attachment component comprises a tracker interface. Theposition and orientation of the tracker interface of the trackerrelative a position and orientation of a transmitter of the tracker ispredetermined and known to the navigation system. The navigation systemreports the position and orientation of the tracker interface of thetracker. According to a method, position and orientation of theinstrument is tracked by tracking the position and orientation of thetracker interface of the attachment component.

BACKGROUND OF THE INVENTION

Orthopedic replacement systems, such as hip, knee, foot and ankle,shoulder, elbow, and spine replacement systems are commonly available.These systems comprise implants including various components for totalreplacements of a piece of the patient's anatomy. Each system comprisesa range of components, including various sizes. For example, a hipreplacement system can comprise an acetabular component, which includesan acetabular shell, and acetabular insert, and a bearing, and thefemoral component, which includes the femoral stem. The systems can becemented or press-fit. Furthermore, a wide variety of system specificinstruments are used with each replacement system. Again taking a hipreplacement system as an example, such as system may include instrumentsincluding osteotomes, reamers, saws, handles, planars, reamers, steminserters, stem impactors, head impactors, chisels, broach handles, andtrial components. Many times, the instruments are combined in kits,which include the required instrumentation for a particular replacementsystem. The instruments are to a large extent for multiple use.

Different replacement systems may be available on different markets. Oneach market, a number of competitive replacement systems are oftenavailable. On top of this, different replacement systems are availablefor the various surgical fields exemplified above. In summary, thatmeans that there are a large number of replacement systems, and an evenlarger number of implant components and instruments, available on theglobal market. Providing a generic navigation system that is applicableto all of these replacement systems is challenging.

Surgeons generally select to work with a few replacement systems for aparticular surgical intervention, such that a replacement surgerysuitable to the individual patient can be provided. This means that thesurgeon can have the required instruments available, and have a limitednumber of implant components in stock to be able to select amongst a fewsuitable implant components during surgery. Since the surgeon only workswith a limited number of replacement systems, the surgeon can masterthese replacement systems in order to perform a surgery at the best ofhis/her ability. Yet, there are a large number of surgical interventionswhere the implant components are positioned in non-optimal positions,with non-optimal surgical outcome for the patient. Hence, there is aneed for improvement of the positioning of implant components fororthopedic replacement systems. However, the surgeon do not want to workwith different surgical navigation systems that are each specific for asingle replacement system. Instead, the flexibility to select the mostappropriate navigation system is desired and at the same time use thereplacement system with which the surgeon is familiar.

Various Computer Assisted Orthopedic Systems (CAOS) exist, which rangefrom active robotic to passive or navigation systems. Active roboticsystems are capable of performing surgery autonomously withoutinteraction by the surgeon. Semi-automatic robotic systems also exist,which give the surgeon more freedom, but still within certainlimitations. Many times, the surgeon wants to be in control of thesurgery. In such situations, passive or semi-automatic navigationsystems are preferred, which provide additional information during aprocedure compared to conventional surgery but do not perform thesurgical action. The surgeon controls the intervention but acts onadditional patient information obtained from a pre-operative scan.During surgery with a robotic system, the surgical instrument is not inthe hands of the surgeon but carried by a robot, which is onlyindirectly controlled by the surgeon.

Common to the robotic and surgical navigation systems is that they usesome type of passive or active marker, which a receiver or locator canfollow in real time. Many of these systems use a number of passivegeometrical objects, such as spheres, arranged in a particular patterfrom which the instruments' position and orientation in space can betracked. These geometrical objects have a predefined fixed relationshiprelative the position and orientation of the end effector of thesurgical instrument. Therefore, also common to these robotic andsurgical navigation systems is that system specific surgical instrumentsare required for each navigation system to accurately and reproduciblyalign implant components with the pre-operative plan. That means, inorder for a surgeon who wants to use a navigated replacement system inorder to improve the accuracy of replacement component positioning, butwho currently uses a particular replacement system that is not designedfor surgical navigation, the surgeon has to switch to a new unfamiliarreplacement system, including new an unfamiliar instruments.Furthermore, if the surgeon currently is using multiple replacementsystems that are not navigated, the surgeon may be limited to choose asingle navigated surgical replacement system, since it is noteconomically viable to have multiple navigated replacement systems, itis simply too expensive. The navigated replacement system may provide abetter surgical outcome, but still not be optimal. Even an experiencedsurgeon will be, at least initially, inexperienced with a new surgicalnavigation system. Therefore, there exists a need for a surgicalnavigation system that can be used with any orthopedic replacementsystem, also non-navigated replacement systems, already available on themarked and with which the surgeon is already familiar, such that thesurgeon does not need any training on the replacement system, with whichhe/she is already experienced.

WO2011134083 discloses systems and methods for surgical guidance andimage registration, in which three-dimensional image data associatedwith an object or patient, is registered to topological image dataobtained using a surface topology imaging device. The surface topologyimaging device may include fiducial markers, which may be tracked by anoptical position measurement system that also tracks fiducial markers ona movable system specific instrument. The system specific instrument maybe registered to the topological image data, such that the topologicalimage data and the movable system specific instrument are registered tothe three-dimensional image data. The system may also co-register imagespertaining to a surgical plan with the three-dimensional image data. Thefiducial markers may be tracked according to surface texture. The systemutilizes fiducial markers attached to system specific surgicalinstruments that have a fixed relationship relative to an end-effectorof the instrument. Hence, the system becomes complicated and expensive,since system specific surgical instruments with fiducial markers arerequired. The position of the end-effector of the surgical instrument isdetermined and recorded using a 3D model of the surgical instrument,which is imported from computer aided design (CAD) drawings, in whichthe instrument tip is known. Alternatively, the surgical instrumentincluding the fiducial markers can be profiled with a structured lightscanner to obtain its 3D geometry. The instrument tip and orientationaxis are determined from an acquired point cloud. These aretime-consuming processes for obtaining the positions of the instrumenttip relative the fiducial markers, which is undesired during surgicalaction where time is a scarce resource, not only during the surgicalaction itself but also in preparation therefore.

US2009234217A1, US2011251607, and US2007238981A1 disclose variousaspects of navigation systems. However, utilizing various types offiducial markers, they all suffer from at least the same issues as thenavigation system disclosed in WO2011134083, such as in relation to thecalibration of the position of the end-effector or tool-tip relativefiducial markers.

U.S. Pat. No. 5,921,992 discloses intraoperative calibration of anarbitrary surgical instrument relative a surgical navigation digitizingsystem. The system comprises a calibration guide that has markers inknown positions relative a guide tube. Hence, the entire calibrationguide is pre-calibrated relative a camera system and its position isknown in the navigation system. Alternatively, a calibrated guide has achuck that can be closed on a probe end of an instrument. The instrumentis an existing calibrated instrument so that its probe end and tipposition are already known in the coordinate system of the cameras.Inserting the pre-calibrated instrument will determine the position ofthe calibration guide. Then, the pre-calibrated instrument is removedfrom the chuck, and the position of other instruments having the sameshape as the pre-calibrated instrument can be calibrated into thecoordinate system of the cameras by inserting its probe into the chuck.An array of light markers can be directly clamped to the instrumentbefore calibration. This system is very inflexible, since it may only beused together with instruments having identical shapes and positions ofthe probe end. Also, if the calibration instrument is moved, it has tobe re-calibrated. Adding a new instrument, or using the system togetherwith a different replacement system, requires multiple calibrationguides and/or new calibration probes.

U.S. Pat. No. 7,166,114 discloses a surgical navigation system that doesnot require a calibration system to track the axis of an instrument.Instead, a tracker is attached to the instrument using a pre-calibratedadapter. The adapter has a known relation between the coordinate systemof the tracker and the surgical tool or tool axis. This is done byhaving precise knowledge of location of the adapter relative the toolaxis when the adapter is attached to the surgical tool. This requirespre-characterisation of each adapter of the system to each surgical toolwith which it is used. Utilizing the tracker for different replacementsystems, or even surgical tools with different geometrical shapes,requires a database where the location of the surgical tool axisrelative the adapter and tracker coordinate system is stored. Theadapter and tracker have to be characterised in the same coordinatesystem. Adopting the navigation system to new replacement systems orsurgical instruments is complex, expensive and time-consuming andrequires precise characterization of each adapter.

US2005/0288575 recognizes that adapters such as described in U.S. Pat.No. 7,166,114 are expensive and time-consuming to develop. The solutionis to have an adapter that is coupled to a surgical tool in a non-fixedmanner, and can be calibrated by moving the adapter along the tool axis.It is only possible to track the tool axis, but not the end-effector ofthe tool. Also, it is only possible to track position, not orientation.Similar to other adapter based systems, the navigation system knows theidentity of the particular adapter and the surgical instrument. Thesystem is queried with regard to the dimensions of the interface andchannel configuration of the adapter, and the dimensions of the surgicaltool and its effector axis. Hence, the adapter needs to bepre-calibrated, i.e. its shape between an interface for attaching thetracker to the adapter and an interface for coupling the adapter in anon-fixed manner to the surgical tool is known and stored in a database.Again, this system requires pre-characterisation of each adapter of thesystem to each surgical tool with which it is used, with the samechallenges as with regard to the system of U.S. Pat. No. 7,166,114.

Hence, an improved surgical navigation method and system and associatedattachments would be advantageous, and in particular allowing forimproved guidance, precision, increased flexibility, cost-effectiveness,calibration and/or patient safety for use together with any orthopedicreplacement system and surgical instruments of arbitrary shape availableon the market would be advantageous.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the present invention preferably seek tomitigate, alleviate or eliminate one or more deficiencies, disadvantagesor issues in the art, such as the above-identified, singly or in anycombination by providing the method and system according to the appendedpatent claims.

Embodiments comprises an attachment component for attaching a tracker ofa navigation system to an instrument that comprises a body, aninstrument interface attached to the body and configured for detachableattachment of the attachment component to an instrument or implant, atracker interface attached to the body and having a fixed pre-definedshape for engagement with a calibrated tracker interface of the tracker.The instrument interface has in an arbitrary un-calibrated positionrelative the tracker interface.

At least the body and the instrument interface may be formed as anintegral unit. The instrument interface may comprise at least one recessfor engagement with the surgical instrument. Alternatively oradditionally, the instrument interface comprises at least one clamp forclamping the attachment component to surgical instrument.

At least one of position and orientation of the tracker interface may beadjustable relative the position and orientation of the instrumentinterface.

The fixed predefined shape of the tracker interface may comprise ananti-rotational feature, which is non-circular and non-spherical, foranti-rotational engagement to a surface of the tracker interface of thetracker having a complementary shape. The tracker interface may comprisea locking feature, for locking engagement of the tracker interface to atracked surface of the tracker.

Embodiments disclosed herein comprise a set of attachment components.The set may comprise at least two attachment components according to theembodiments of the attachment components disclose herein. The instrumentinterface of at least two of the attachment components may havedifferent geometrical shapes. The tracker interface of at least two ofsaid attachment components have identical geometrical shapes. Eachattachment component of the set may further comprise an electronicallyreadable identifier configured to identify at least one of instrumentbrand and instrument type of the surgical instrument, for which theinstrument interface of the attachment component is configured. Theelectronically readable identifier may comprise a transmitter forwirelessly transmitting an identification code unique for said at leastone of instrument brand and instrument type of the surgical instrument,for which the instrument interface of the attachment component isconfigured.

Embodiments disclosed herein also comprise a combination of anattachment component according the disclosed embodiments and acalibration station having a tracker interface identical to the trackerinterface of the attachment component. The calibration station may beassociated with a known calibration location for an end effector of aninstrument. The tracker interface of the calibration station has a fixedposition relative the calibration location. A tracker is attachable tothe tracker interface of the calibration station. The combination mayalso comprise an instrument, and at least two trackers of a navigationsystem. Each tracker may comprise a tracker interface with a trackablesurface having a pre-defined shape and location. The instrumentinterface of the attachment component may be attachable to theinstrument, a first tracker may be attachable to the tracker interfaceof the attachment component, and a second tracker may be attachable tothe tracker interface of the calibration station.

Embodiments disclosed herein comprises a navigation system comprising atleast one tracker attachable to an instrument to be tracked, a localizerfor tracking at least one of position and orientation of the at leastone tracker; and at least one tracker that comprises a positiontransmitter and a tracker interface for attaching the at least onetracker to the instrument. The navigation system is arranged to reportposition and orientation of the tracker interface of at least one of thetrackers. The navigation system may be a surgical navigation system andthe instrument may be a surgical instrument.

Embodiments disclosed herein comprise a method for tracking position andorientation of an instrument using a navigation system including aplurality of trackers and a localizer for identifying the position andorientation of the tracker. The method comprises receiving identity datafrom at least one tracker of the navigation system, said trackeridentity data being unique for each tracker in the navigation system;receiving position and orientation data of a tracker interface beingattached to a tracker interface of an attachment component; obtainingcalibration data defining the position and orientation of a portion ofthe instrument relative a tracker interface of the attachment component;and translating the position and orientation data of the trackerinterface into position and orientation data of the instrument usingsaid identity data and said calibration data.

Embodiments disclosed herein comprise a computer program product storedon a computer usable medium, comprising computer readable program meansfor causing a computer to carry out the embodiment of the methodsdisclosed herein when executed.

The embodiments of attachment components, calibrations stations andmethods, and methods for associating a pre-operative plan with trackingdata discloses a system that is flexible and may be adapted to anyorthopedic replacement system already existing on the market. The systemis particularly useful for replacement systems where multipledifferently shaped instruments are used during the course of theintervention. Furthermore, solutions described herein provides forconfiguring the system such that the system may be installed indifferent environments with maintained accuracy and without affectingthe way the surgeon is used to work with the instruments he/she isfamiliar with. The shape of the instruments do need to be known to thesystem. Hence, the attachment components and trackers do not need to becharacterized in the system, which becomes less complex than previoussystems. The embodiments do not impair the capabilities of the existinginstruments; rather the operator gets access to real time data as wellas data from a pre-operative plan that enhances the use of theinstruments for a better outcome of the procedure. Furthermore, thesystem can be adapted to any tool of any orthopedic replacement system,even without prior knowledge of its shape. This means that the samesystem may be used by different surgeons for different interventions,only by exchanging attachment components. Different surgeons for thesame intervention can adapt positions and orientations of the componentsto his/her desire without impairing tracking of the instruments. Eventhe position tracker can be positioned in an optimal position, and theposition and orientation of the tracker attached to the instrument beadapted to an optimal position and orientation relative the positiontracker within the specific environment within which the system isdeployed. This means that the system can be used with any replacementsystem in virtually any environment with maintained accuracy while theoperator uses the tools and instruments he/she is familiar with.

Further embodiments of the invention are defined in the dependentclaims.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which

FIGS. 1a-1c are schematic views of a surgical navigation system;

FIGS. 2a-2e are perspective views of attachment components having atracker interface and an instrument interface;

FIG. 3 is a perspective view of a tracker interface of the tracker and atracker interface of the attachment component;

FIG. 4 is a block diagram of a surgical navigation system including anavigation system;

FIGS. 5a-5e are schematic views of a method and a system for associatingposition and orientation of a surgical instrument relative apre-operative plan;

FIGS. 6a-6d are schematic views of a calibration process for calibratingthe position and orientation of an instrument within a navigationsystem;

FIG. 7 is a side view of a tracker attachable to an attachmentcomponent;

FIGS. 8a-8c are side and perspective views, respectively, of a trackerinterface of an attachment component;

FIGS. 9a-9c are side and perspective views, respectively, of a trackerinterface of a tracker in non-aligned, non-locked, and locked positions,respectively, relative a tracker interface of an attachment component;

FIGS. 10a-10d are side-views of embodiments of calibration objectsattached to surgical instruments; and

FIGS. 11a-11b are perspective views of embodiments of calibrationobjects.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

The following description focuses on embodiments of the presentinvention applicable to a surgical navigation system. However, it willbe appreciated that the invention is not limited to this application butmay be applied to many other procedures, such as other navigationsystems where the position and/or orientation of an object is tracked.The examples given in the below embodiments relate to a hip replacementsurgery and spine surgery. Other embodiments include knee surgery, spinesurgery, elbow surgery, ankle surgery, and other replacement surgeries.

In the below embodiments, reference is made to tracking position andorientation of instruments. In this context, the term instruments, inaddition to instruments for the surgical examples given herein, includeimplant components, such as for replacement of patient anatomy or addinginto the patient anatomy, as well as for temporary attachment ofcomponents of the replacement system during the surgical intervention.Such temporary components may include threaded screws or unthreadednails for temporary attaching trackers to the patient anatomy duringsurgery in the same way as the trackers are attached to the attachmentcomponents, as will be described herein. Furthermore, instrumentsinclude surgical guides that may attached to the anatomy or implants forguiding the instrument or checking accuracy of an installed implant,such as checking rotation, position, and/or orientation of an implant.

FIGS. 1a-1c illustrate embodiments of a surgical navigation system.Parts of this system have been disclosed in patent application no.PCT/SE2013/050952 by the same applicant as the applicant of the presentinvention, which is incorporated herein in its entirety for allpurposes. The surgical navigation system of patent application no.PCT/SE2013/050952 has been further improved by embodiments of thepresent invention.

The surgical navigation system comprises a calibration unit 1.Furthermore, the navigation system comprises at least two trackers 2 a,2 b, 2 c, 2 d, 2 e. In the present example, five trackers 2 a-2 e areillustrated. However, a particular tracker may be moved between variousinstruments 3 a, 3 b depending on the particular work-flow of thesurgery at which the system is used. The complete system may be usedwith only two trackers 2 a-2 e. A particular tracker 2 c, 2 d may alsobe attached to an implant, e.g. a temporary screw or nail, which in turnis attached to patient anatomy for tracking position and orientation ofthe patient anatomy during surgery. A tracker may also be attached to animplant to guide positioning of the implant and/or check positing andorientation of the implant after it has been seated. The calibrationunit 1 may be adapted to calibrate at least one of position andorientation of any tracker 2 a-2 e associated with an instrument orimplant within the surgical navigation system. Calibrating the trackerposition and/or orientation allows for calibrating the position andorientation of the surgical instrument 3 a, 3 b, such as an end-effectorand/or axis thereof. The surgical navigation system is provided withinthe surgical theatre or operating room.

FIG. 1b illustrates an instrument 3 a in the form or a probe, which maybe used to locate the position of various structures, e.g. patientanatomy, landmarks, etc. which have a correspondence in a preoperativeplan such that the structure can be registered to a correspondingvirtual structure in a preoperative plan. Such a virtual structure maycomprise a surface representation of patient anatomy obtained from CTdata.

FIG. 1c illustrates tracking the position and/or orientation of asurgical instrument 3 b. The surgical navigation system also comprises afeedback unit, such as a display 4. The patient structure may be alignedwith the virtual structure during a registration process. Utilizing thecomponents of the surgical navigation system, the position andorientation of the surgical instrument 3 b relative to the pre-operativeplan and the patient structure may be tracked in real-time, such asillustrated in FIG. 1c , wherein the position and orientation of avirtual representation of the surgical instrument is displayed inrelation to the virtual structure in the preoperative plan in the samerelationship as the surgical instrument 3 b to the patient structure inreal-time. A straight line representing the axis of the surgicalinstrument 3 a may be shown as the virtual representation on the display4 relative the virtual object. The pre-operative plan may be providedfrom a software module for planning a surgical intervention based on CTor other 3D patient specific data including data of the anatomy subjectof the surgery. The virtual representation of the surgical structureshown on the display 4 may be surface models segmented based on thepatient specific data. The display 4 and surgical navigation system maybe connected to and implemented by a computer 5 for processing data fromthe navigation system. The computer 5 may render the pre-operative planand the position and orientation of tracked instruments 3 a-3 b relativethe pre-operative plan. A position tracker 6 or localizer, such as anarray of cameras or receiver of radio based position data, is configuredto track current position and/or orientation of the trackers 2 a-2 e inits area of coverage.

According to embodiments, the tracker 2 a-2 e comprises a trackerinterface, i.e. an attachment interface, for attaching the tracker toanother object in a fixed position. The coordinate system of eachtracker 2 a-2 e is defined relative the tracker interface. Other objectsor structures of the tracker are calibrated or characterized against thetracker interface. This means that the tracker can track an object, suchas an instrument, of arbitrary shape and be attached at an arbitraryposition relative to the object. For example, the tracker interface maycomprise a chuck. In the embodiments of a surgical navigation system,this means that the tracker can be attached to any surgical instrumentat any position thereof, to which the chuck can be attached. This, inturn, means that the navigation system can be easily adapted to trackcomponents of any replacement system, such as surgical instruments andimplants. Hence, the surgical navigation system is very flexible.

In order to make the system even easier to implement, and/or configureto a replacement system that has not been previously supported,embodiments of the present invention comprises an attachment component.The attachment component provides a precise tracker interface on aninstrument that does not have such a tracker interface when it was made.Hence, replacement systems already available can be retrofitted with anavigation system. The attachment component can be produced by rapidproductions techniques, such as 3D printing. It may be designed suchthat it fits to the instrument in a position where it may be fixed, andthe attachment component and instrument form a rigid body, at leasttemporarily.

FIGS. 2a-2e illustrate various attachment components 10 a-10 d forattachment of a tracker 2 a-2 e to different objects, such as surgicalinstruments 14 a-14 c or implants. In the following, reference is madeto an instrument as an example of an object, but may equally be animplant or other object of a replacement system.

The attachment component 10 a-10 d is provided for attaching the trackerto the instrument such that the tracker 2 a-2 e, the attachmentcomponent 10 a-10 d, and the instrument 3 a-3 b forms a rigid body inuse. The attachment component 10 a-10 d may be retrofitted into a fixednon-moveable position relative the instrument such that the position andorientation of the instrument may be tracked by tracking the positionand orientation of the tracker 2 a-2 e. The position and orientation ofthe tracker relative the instrument is arbitrary and does not need to beknown.

Each attachment component 10 a-10 d comprises a body 11 a-11 d, aninstrument interface 12 a-12 d, and a tracker interface 13 a-13 d. Theinstrument interface 12 a-12 d is attached to the body 13 a-13 d. Also,it may be configured for detachable attachment of the attachmentcomponent to the surgical instrument 3 a-3 b, such as at a predefinedposition and orientation. Hence, the tracker is not moveable relativethe instrument 3 a-3 b while it is tracking the instrument 3 a-3 b.However, it may be removed at other times, such as during sterilizationof the instrument 3 a-3 b. The attachment component may be delivered asa pre-sterilized consumable or be a sterilizable multiple-use component.

Furthermore, the tracker interface 13 a-13 d may be attached to, such asformed integral with or be connectable to, the body 13 a-12 c. Thetracker interface 13 a-13 d may have a fixed pre-defined shape forengagement with a tracker interface of the tracker, which may becalibrated. This means that the attachment component 10 a-10 d, and anyobject attached in an arbitrary position and orientation thereto aredefined relative the tracker interface 13 a-13 d of the attachmentcomponent 10 a-10 d. Furthermore, the instrument interface 12 a-12 d hasan arbitrary un-calibrated position relative the tracker interface 13a-13 d. Hence, the navigation system does not know the position andorientation of the instrument interface 12 a-12 d relative the trackerinterface 13 a-13 d. This is possible since the coordinate system of thetracker 2 a-2 e is provided at a location that may be shared by thetracker interface of the tracker 2 a-2 e and the tracker interface 13a-13 d of the attachment component 10 a-10 d. The body 11 a-11 d, theinstrument interface 12 a-12 d, and the tracker interface 13 a-13 d ofthe attachment component 10 a-10 d may form a rigid body in use. Hence,the tracker 2 a-2 e, the attachment component 10 a-10 d, and theinstrument 3 a-3 b form a rigid body unit in use when the tracker 2 a-2e is attached to the tracker interface 13 a-13 d of the attachmentcomponent 10 a-10 d and the instrument 3 a-3 b is attached to theinstrument interface 12 a-12 d to provide a fixed relationship betweenthe tracker interface of the tracker 2 a-2 e and the surgical instrument3 a-3 b.

In some embodiments, the instrument interface 13 a-13 d is arranged atan arbitrary un-calibrated position and orientation relative the trackerinterface 13 a-13 d. This arbitrary un-calibrated position andorientation may be adjustable, such as to different fixed relativepositions and/or orientations. In order for the tracker interface 13a-13 d to form a rigid body with the body 11 a-11 d and the instrumentinterface 12 a-12 d, the adjustable arbitrary un-calibrated position andorientation may be locked at different positions and orientations suchthat the tracker interface 13 a-13 d has a fixed position andorientation relative the body 11 a-11 d in use. This provides forarranging the tracker 2 a-2 e in an optimal position and orientationrelative the position tracker 6 independent of the position andorientation of the position tracker 6. For example, the layout or theoperating room and other surgical equipment may impose restrictions onthe position and orientation of the position tracker 6. It may need tobe positioned differently relative the patient in different operatingrooms, or even in the same operating room depending on thecircumstances, type of surgical procedure etc. That means that the lineof sight between the position tracker 6 and the tracker 2 a-2 e when thesurgeon uses the instrument may be sufficient at one position of theposition tracker 6, but blocked from another positions of the positiontracker 6 if the relative position of the tracker interface 13 a-13 d isfixed and not adjustable. On the other hand, when the tracker interface13 a-13 d is adjustable relative the instrument interface 12 a-12 d, theposition and orientation of the tracker 2 a-2 e, when attached to theinstrument 3 a-3 b, relative the position tracker 6 can be adjusted toan optimal position for a clear line of sight while instrument can beused as desired. The same applies if different surgeons orient the sameinstrument differently during use. The tracker 2 a-2 e can be arrangedat an optimal position for a clear line of sight for each surgeon.Hence, the system is more flexible. Once the position of the trackerinterface 13 a-13 d relative the instrument interface 12 a-12 d has beenadjusted and locked, calibration may commence as is described below.

At least the body 11 a-11 d and the instrument interface 12 a-12 d ofthe attachment component 10 a-10 d may be formed as an integral unit.Hence, precision and accuracy is provided for. Furthermore, theinstrument interface 12 a-12 b may comprise at least one recess 20 b-20d for engagement with the surgical instrument, such as is illustrated inFIGS. 2b, 2d and 2e . The instrument interface 12 a-12 d may have ashape that is specific for each instrument, such as a shape that iscomplementary to the shape of an exterior surface of the instrument.This enables a stable and fixed attachment of the attachment component11 a-11 d. However, the position and orientation of the trackerinterface 13 a-13 d of the attachment component 11 a-11 d may still beunrelated to the position and orientation, and thus shape, of theinstrument. This also provides for precision and reliability, such thatthe components may not be disengaged by mistake and such that thecoordinate system of the tracker 2 a-2 e is shared at the respectivetracker interfaces 13 a-13 d.

Alternatively or additionally, the instrument interface 12 a-12 d of theattachment component 10 a-10 d may comprise at least one clamp forclamping the attachment component 10 a-10 d to the instrument 3 a-3 b.In the embodiment of FIG. 2b , the instrument interface 12 b is annularwith a recess in the axial direction of the instrument and though thebody in order to provide sufficient flexibility to the body 11 b suchthat a snap fit connection is provided. The snap-fit instrumentinterface may have a ridge or rim that engages an annular recess of thesurgical instrument 14 b. In the embodiment of FIG. 2d , the recess 20 cprovides an opening for inserting a shaft of the surgical instrument 14c, such as a spine punch tool. Also illustrated with regard to thisembodiment is a handle of the surgical instrument received in theinstrument interface 12 c. The handle is in this embodiment sphericalwhereas the instrument interface is part spherical. Hence, the shape ofthe instrument interface 12 c may at least partly conform to a shape ofa handle of the instrument 14 c. Other shapes of the handle areconceivable.

As is illustrated in the embodiment of FIG. 2a , the attachmentcomponent may comprise a recess 15 that extends around, or partiallyaround, the body 11 a. The recess may be sized and configured to receivea tie or band, such as a rubber band or cable tie, that wraps around thebody 11 a and a portion of the instrument, such as a handle thereof. Thetie or band and instrument interface forms a clamp for clamping theattachment component 10 a to the instrument 14 a.

FIG. 2e illustrates an embodiment wherein at least one of position andorientation of the tracker interface 13 d is adjustable relative theposition and orientation of the instrument interface. To the left inFIG. 2e , the tracker interface 13 d is attached to the attachmentcomponent 10 d, and to the right, the tracker interface 13 d is detachedfrom the attachment component 10 d. For example, the tracker interfacemay be attached to a base, as will be described below. A stud orprotrusion (not shown) may extend from the base in the longitudinaldirection of the tracker interface 13 d, and be received in a recess 21d of the body 11 d. In the illustrated embodiment, the recess 21 d andstud are cylindrical such that the tracker interface 13 d may be rotatedrelative the longitudinal axis of the instrument interface 12 d, wherebyits position and/or orientation is adjusted.

The body 11 d may comprise several recesses for receiving the stud.Hence, also the position of the tracker interface 13 d relative theinstrument interface 12 d may be adjusted. The tracker interface 13 maybe fixed in a desired location and orientation relative the body 11 d,such as by applying an adhesive in the recess 21 d. Additionally oralternatively, a press fit connection between the stud and recess 21 dmay provide sufficient fixation of the tracker interface 13 d such thatit does not move during operation of the instrument. In this embodimentas well as in the embodiment of FIGS. 2c-2d , the body 11 c-11 dcomprises a surface 22 d that is non perpendicular relative theinstrument interface 12-c-12 d. Hence, the longitudinal axis of thetracker interface 13 c-13 d will be non-parallel to the longitudinalaxis of the instrument, and improved line of sight may be obtained.Furthermore, the body 11 c-11 d may comprise multiple suchnon-perpendicular surfaces 22 c-22 d at which the tracker interface 13c-13 d may be attached to the body 11 c-11 d to accommodate fordifferent situations, wherein each surface 22 c-22 d may comprise atleast one recess 21 d for receiving the stud.

Furthermore, in some embodiments, the base of the tracker interfacecomprises a lockable swivel joint, by means of which the trackerinterface 13 a-13 d may be rotated and/or tilted relative the instrumentinterface 12 a-12 d. Such a swivel joint may be provided by a ballreceived in a seat or socket, and the ball locked to the socket by ascrew or nut pressing the ball towards the socket to a locked position.The swivel joint provides for an adjustable position and/or orientationof the tracker interface 13 a-13 d.

As is illustrated in FIG. 2e , the body 11 d may have a recess 20 dextending in the longitudinal direction of the instrument interface 12 dwhereby two arms are formed by the body that extends transverse to theinstrument interface. The instrument may be received into the instrumentinterface 12 d through the recess 20. The instrument interface 20 d maybe clamped to the instrument by tightening the arms around theinstrument. The arms may be tightened by a snap fit connection, or by abolt (not shown) received in a recess 23 d transverse to the arm. Thehead of the bolt may be received in one of the arms, and a nut orthreads provided in the other arm. Closing the arms will clamp theattachment component 10 d to the instrument.

The attachment component may be made by a sterilizable material, such asmedical grade plastics or metal. Components made of medical gradematerial are particularly suitable for rapid prototyping, such thatattachment components easily can be manufactured and navigation ofadditional instruments made possible without any adaptation of othercomponents of the navigation system or databases in the system.

FIG. 3 illustrates an embodiment of the tracker interface 24 of theattachment component and the tracker interface 25 of the tracker (theattachment component and tracker are not illustrated in FIG. 3). A fixedpredefined shape of the tracker interface comprises an anti-rotationalfeature, which may be non-circular and non-spherical. This provides fanti-rotational engagement of a surface of the tracker interface 25 ofthe tracker to a surface of the tracker interface 24 of the attachmentcomponent having a complementary shape. In this embodiment, theanti-rotational feature of the tracker interface 24 of the attachmentcomponent is a flat or planar surface of an otherwise cylindrical orconical surface. The flat surface extends in the longitudinal directionof the tracker interface 24, 25. Alternatively, the anti-rotationalfeature may be a surface that is square, hexagonal, star shaped, oval,wave shaped or any other non-circular shape in a cross section takenalong the longitudinal axis of the tracker interface 24. The trackerinterface 24 of the attachment component may comprise a protrusionhaving a base 27, or extending from a base surface, and a top 28. Thebase 27 may be wider than the top 28. Hence, an envelope surface 29,which extends from the base 27 to the top 28, may be conical, such thatthe tracker interface 23 forms a truncated cone, which may comprise theflat side surface. In some embodiments, the envelope surface 29 iscircular such that the tracker may be rotated around the protrusion to asuitable orientation relative the instrument before it is locked to theattachment component. This contributes to the flexibility of the system.A recess or protrusion may be provided in the envelope surface 29 atleast partly around the circumference of the protrusion, and which maybe transverse to the longitudinal axis of the tracker interface. Alocking element of the tracker interface 25 of the tracker may engagethe circumferential protrusion or recess. The locking element maycomprise an eccentric member that engages the circumferential recess, aswill be discussed below.

The tracker interface 25 of the tracker may comprise a boss 30 with agenerally flat or planar end surface 31, which may be part of or form atip of the tracker, and a recess 32, which is indicated with phantomlines. The recess 32 may have a shape that is at least partiallycomplementary to the shape of the envelope surface 29, such that thetracker interface 25 provides a location fit, i.e. the tracker interface24 of the attachment component does not move relative the trackerinterface 25 of the tracker when the tracker interfaces 24, 25 arecompletely seated. As is indicated in FIG. 3, the origin or zero point33 of the coordinate system of the tracker may be located at the centerof the boss 30 or recess 32. In the embodiment of FIG. 3, the origin 33of the coordinate system of the tracker is located at a plane coincidingwith a plane formed by the flat end surface 31. When the trackerinterfaces 24, 25 are connected, the base 27 will abut the end surface31. Hence, by tracking the end surface, components in the system may berelated to this surface in order to provide transformation of theposition and or orientation of other components rigidly attachedrelative the tracker.

The tracker interface 23 of the attachment component comprises a lockingfeature, for locking engagement of the tracker interface to a trackedsurface of the tracker, which may be formed by the end surface 31. Thetracker interface 25 of the tracker may comprise a chuck, as will bediscussed below.

The tracker interface of the attachment component has been disclosed ashaving a protrusion and the tracker interface of the tracker as having arecess for receiving the protrusion. In other embodiments, the system isreversed such that the tracker interface of the attachment componentcomprises the boss and recess and the tracker interface of the trackercomprises the protrusion and base.

Returning to FIGS. 2a-2d , embodiments of the invention comprises a setof attachment components. The set of attachment components may compriseat least two attachment components as described herein. The instrumentinterfaces of at least two of the attachment components have differentgeometrical shapes. Hence, each instrument interface is configured for aspecific instrument that is used during a particular surgical procedure.However, the tracker interfaces of at least two of attachment componentsof the set have identical geometrical shapes. The set of attachmentcomponents may be configured for instruments and/or implants of aparticular surgical procedure. As such, the set may be provided as a kitfor each surgery, together with or separate from the implants. A singletracker may be selectively attached to each attachment component of theset during the procedure. Hence, the number of trackers in the systemmay be reduced compared to having a tracker for each instrument orattachment component.

Each attachment component may further comprises an electronicallyreadable identifier configured to identify at least one of instrumentbrand and instrument type of the instrument, for which the instrumentinterface of the attachment component is configured. The electronicallyreadable identifier may comprise a transmitter for wirelesslytransmitting an identification code. Such an electronically readableidentifier may include an RFID tag, a bar code, a QR code, or similarcode that is electronically readable. If the system identifies that theattachment component is not configured for a particular replacementprocedure, the system may present warnings. For example, a warning mayindicate that a particular replacement component may not be accuratelyor reliably attached to the instrument to be used for the surgery. Theinstrument to be used may be defined in the system or in a preoperativeplan.

FIG. 4 illustrates main components of a surgical navigation system 40.The surgical navigation system may comprise a navigation system 41, aCAD module 42, the attachment components 10 a-10 d and a calibrationstation 43, which will be further described below. The CAD module 42 maycomprise patient specific volumetric data and object models based on thevolumetric data. The CAD module 42 may also comprise a pre-operativeplan, in which implant component positions and orientations and/orinstrument paths have been defined relative the patient specific data.The navigation system 41 can be provided as a stand-alone componentwithin the surgical navigation system 40. This means that the navigationsystem provides to the CAD module 42 the position and orientation ofeach tracker interface of each tracker 2 a-2 e in the area of coverageof the navigation system 41. Furthermore, the navigation system 41 mayprovide data of the position and orientation of a tracker interface of atracker attached to a calibration station, as will be discussed below.At calibration, the CAD module 42 may generate a transformation databaseor table for each attachment component and instrument combination, suchthat the position and orientation of a tracked surface of the attachmentcomponent 10 a-10 d is known for determining position and/or orientationof the surgical instrument 3 a-3 b. The tracked surface of theattachment component 10 a-10 d may be the base surface 27 of the trackerinterface 24. Hence, the navigation system 41 only needs to report theposition and orientation of the tracker interface 25 of the tracker,which mates with the tracked surface of the attachment component 10 a-10d. This means that the surgical navigation system 40 is independent ofthe technology of the navigation system 41. The only requirement of areplacement navigation system 41 is that it reports the position andorientation of the tracker interface, and potentially tracker identitydata as will be discussed below, and that the replacement navigationsystem has a tracker interface that corresponds to the old trackerinterface and fits the tracker interface of the attachment component.Hence, the surgical navigation system is very flexible. Furthermore,combinations of attachment components and instruments can be added tothe surgical navigation system at any time by calibrating the attachmentcomponent and instrument combination, as will be described below. Thismakes the system very easy to adapt to new replacement systems and newinstruments made available to already supported replacement systems.

As is illustrated in FIG. 5a , the tracker 2 b may be attached to thesurgical instrument rather than a surgical tool 33, such as a drillingmachine, a planar machine, a sawing machine etc. This means that thesurgeon may use the same machine for different interventions during thesurgical procedure, and may simply disconnect the surgical instrumentand attach a new surgical instrument without having to calibrate theinstrument and attachment component combination, wherein flexibility ofthe system is maintained. A set of attachment components is useful inthis situation. Furthermore, FIG. 5a illustrates a surgical navigationmodule that may comprise the CAD module 42 and the display 4, as will befurther described below.

FIGS. 5b-5e illustrate embodiments of a method and system forassociating the pre-operative plan with position and orientation of thesurgical instrument 3 a, 3 b, such as by the CAD module 42. Thepre-operative plan may be generated in a planning module. Such aplanning module has been described in PCT/SE2013/051210, by the sameapplicant as the applicant of the present invention and which isincorporated herein by reference in its entirety for all purposes. Thepre-operative plan comprises patient anatomy data, such as a scan dataincluding the patient anatomy, for example bony anatomy of the patient.Such scan data may comprise volume imaging data, such as CT data, MRIdata, PET data, SPECT data etc. The pre-operative plan may also compriseplanned position and orientation of an implant and/or surgicalinstrument relative the patient anatomy data. The pre-operative plan mayalso comprise trajectories of the surgical instrument for a plannedoutcome, such as the trajectory of a cut or drilling action.Furthermore, the pre-operative plan data may comprise surface models,such as STL models, generated based on the patient anatomy data. Thepre-operative plan may also comprise a combination of the indicated datatypes. Hence, the pre-operative plan comprises large sets of data thatthe surgeon may benefit from during the surgical procedure but whichhe/she has previously not had access to during the surgicalintervention. The surgeon can simply not see beyond the surfaces exposedduring the surgical intervention, and cannot imagine any structurehidden by the exposed surfaces. The present embodiments provide accessto patient data available during a pre-operative planning process, butnow during the surgical intervention without having to manually interactwith the pre-operative plan. The pre-operative plan may be apre-operative plan of a hip, a spine, such as spine fusion, pediclescrew placement, orthopedic joint surgery, an foot and ankle, shoulder,or elbow surgery.

The pre-operative plan is not described in further detail herein. Forfurther details of the pre-operative plan, reference is made toPCT/SE2013/051210. The pre-operative plan may e.g. be imported into theCAD module 42. Alternatively or additionally, a module for preparing thepre-operative plan is provided as a module within the CAD module 42.

Initially, the pre-operative plan is not associated with the positionand orientation of the surgical instrument 3 a, 3 b. Embodiments hereinprovide a system and a method, wherein the pre-operative plan isassociated with the position and orientation of a tracked surgicalinstrument. According to these embodiments, a link is provided betweenthe pre-operative plan and the navigation system while the instrument isused. Hence, the system can continuously update a virtual representationof the pre-operative plan while the surgeon moves the surgicalinstrument. Hence, the system makes the pre-operative plan useful alsoduring use of the instruments that are planned for in the pre-operativeplan.

The surgical instrument may comprise a probe to locate a particularlandmark. The surgical instrument may also comprise a surgical template,such as a template to be attached to an implant or anatomical structurein order to indicate its position and/or orientation. Hence, the methodmay be non-invasive and exercised by a non-medically trained operator.In the following, reference is made to a surgeon, but this may equallybe a non-medically trained operator. The embodiments provides a userfriendly system, wherein user interaction with the system is minimizedand still the surgeon can benefit from the data that was used during thepre-operative plan in real time during surgery. Since this may becombined with the surgical navigation system presented herein, thesurgeon may operate with conventional tools that he/she is familiar withbut guided by enhanced information that was also used during apre-operative planning process.

The method and system for associating a pre-operative plan with trackedposition and orientation of the instrument will now be described inrelation to FIGS. 5b-5e , which disclose various embodiments of themethod and system.

A pre-operative plan including patient anatomy data is provided. In someembodiments, the pre-operative plan includes only patient anatomy data,such as scan data. An instrument is associated relative the patientanatomy data only such as relative bone tissue of the anatomy data. Thisis useful e.g. in order to locate various structures of the patientwithout having to manually manipulate the patient data on a display. Itis difficult to manually orient the patient data in the system such thatit is oriented relative to an instrument using an input device, such asa mouse. The instrument in such an embodiment may be a pointer or probe.In other embodiments, the preoperative plan comprises planned positionand orientation of a surgical object relative the patient anatomy data.The surgical object may be an implant, surgical guides, surgicalinstruments, incision or cutting lines or planes etc. i.e. an objectthat is external to the patient anatomy data and/or external to scandata of the patient.

The pre-operative plan may be imported into the CAD module 42, such asindicated above. The position and orientation of a patient anatomywithin the navigation system is obtained, such as by the navigationsystem, when a tracker is attached to the patient anatomy. Also, thepatient anatomy is referenced to a virtual representation of the patientanatomy data in the preoperative plan using the navigation system, suchas has been described above. The patient anatomy and the virtualrepresentation of the patient anatomy may be dynamically referenced suchthat position and orientation of the patient anatomy is continuouslytracked and displayed on the display 4.

The tracking data contains information of position and orientation ofthe instrument 3 a, 3 b within the navigation system, such as isdescribed herein, i.e. relative the patient anatomy.

The method and system for associating the pre-operative plan with thetracking data comprises a split window 50. The split window comprisesseparate parts 51 a, 51 b, 51 c, 51 d. Multiple virtual representationsof the surgical instrument 52 are generated relative multiple virtualrepresentations of the pre-operative plan depending on the trackingdata. Each virtual representation of the surgical instrument 52 isgenerated in relation to a virtual representation of the pre-operativeplan in one part of the split window 50. The multiple virtualrepresentations of the pre-operative plan are updated based on theposition and orientation of the instrument, i.e. they are dependent onthe tracking data. Different aspects of the pre-operative plan may bedisplayed in the separate parts 51 a, 51 b, 51 c, 51 d depending on theposition and orientation of the instrument relative the patient anatomy.This provides the surgeon with different types of data and/or differentviews of the same data without having to manually interact with thesystem, which is controlled by the tracked position and orientation ofthe instrument. This makes the system more intuitive and flexible torequirements of different replacement systems and procedures. Differentreplacement systems or procedures may require access to different typesof data. This is catered for with embodiments of the system forassociating the pre-operative plan with the tracking data.

As is illustrated in FIG. 5c , the virtual representation of thepre-operative plan may comprise at least one of volumetric data 53(smaller dots), an object representation 54 (solid white), and greyvalue data 55 (larger dots). These different types of patient data maybe generated simultaneously or separately by showing and hiding thedifferent types of data in any of the separate parts 51 a, 51 b, 51 c,51 d of the split window 50. In FIG. 5b , only volumetric data 53 isshown in all parts 51 a, 51 b, 51 c, 51 d of the split window 50. InFIG. 5d , only grey value data 55 is shown in all parts 51 a, 51 b, 51c, 51 d of the split window 50. The object representation may comprise asurface model, a wire frame, or a solid, generated based on importedvolumetric patient data, implemented using 3D computer graphics, such asthe CAD module 42. Volumetric data 53 may e.g. comprise voxel dataobtained from the pre-operative plan, such as from a stack of CT imagesor MR data including the patient anatomy. Grey value data 55 may becalculated at an arbitrary re-slice plane generated from a stack ofCT-images or from MR data. The virtual representation of thepre-operative plan may also comprise a virtual representation of animplant and/or instrument or instrument trajectory, or any other objectin a planned position and orientation relative the patient anatomy inthe preoperative plan.

Returning to FIG. 5b , at least one display plane 56 a, 56 b, 56 c forgenerating the virtual representation of the patient data is fixedrelative at least one dimension of the virtual representation ofpre-operative plan or the virtual representation of the surgicalinstrument 52. Each display plane 56 a, 56 b, 56 c may be indicated ineach part 51 a, 51 b, 51 c, 51 d of the split window 50 in order toassist the operator in understanding the relative orientation of thedata in each part 51 a, 51 b, 51 c, 51 d of the split window 50. Alldisplay planes 56 a, 56 b, 56 c may visible, such as by a frame, also inthe first part 51 a. In FIG. 5b , the display planes are not visible inthe first part 51 a, whereas they are visible in the first part 51 a inthe embodiment of FIG. 5d . The display planes 56 a, 56 b, 56 c may befilled a solid color, such as black, in order to resemble a tomographicslice of data and/or only show grey value data within the contours of aspecific piece of anatomy, such as bone.

In the embodiment of FIG. 5b , the display planes 56 a, 56 b, 56 c arefixed relative a dimension of an implant component 57 in thepre-operative plan. For example, any of the display planes may 56 a, 56b, 56 c may be fixed relative a landmark of the implant component 57 ofthe pre-operative plan, such as a rotational indicator of the implantcomponent. Such rotation indicators may e.g. be provided on a cup for ahip replacement. This means that the association of the pre-operativeplan and display planes is provided by the type of implant component.Additionally or alternatively, the dimension may be a longitudinal axisand/or a position of the implant component, such as a tip or centerthereof.

The implant component 57 has a fixed planned position and orientationrelative the patient anatomy data. Hence, the display planes 56 a, 56 b,56 c may also be fixed relative the patient anatomy data. The displayplanes 56 a, 56 b, 56 c provide the viewing orientations of the virtualrepresentation of the pre-operative plan in the various parts 51 a, 51b, 51 c, 51 d of the split window 50.

In some embodiments, the display planes 56 a, 56 b, 56 c are fixedrelative a structure of the patient anatomy, such as a landmark of thepatient anatomy, for example a ridge of the patient anatomy. A spinousprocess or a transverse process of a vertebrae may present such alandmark. Also, a portion of the pelvis, such as the acetabulum and/orthe ridge thereof, may present such a landmark.

At least one of the virtual representations of the pre-operative plan iscontinuously updated depending on the tracking data. Also, the virtualrepresentation of the surgical instrument 52 may be continuously updatedin at least one part 51 a, 51 b, 51 c, 51 d of the split window 50depending on the tracking data. As is illustrated in FIG. 5b , a 3Drepresentation of the pre-operative plan is provided in a first part 51a of the split window 50, an axial or transverse representation of thepre-operative plan is provided in a second part 51 b of the split window50 providing an axial or transverse viewing orientation or display plane56 a, a sagittal representation is provided in a third part 51 c of thesplit window 50 providing a sagittal viewing orientation or displayplane 56 b, and a coronal representation is provided in a fourth part 51d of the split window 50 providing a coronal viewing orientation ordisplay plane 56 c. In other embodiments, only one or two of the secondpart 51 b, the third part 51 c, and the fourth part 51 d of the splitwindow 50 are provided in combination with the 3D representation in thefirst part 51 a of the split window 50.

Each display plane 56 a, 56 b, 56 c may be orthogonal to the otherdisplay planes 56 a, 56 b, 56 c. Furthermore, at least one of thedisplay planes 56 a, 56 b, 56 c may be parallel and/or coincide with aresliced plane for generating grey values from volumetric scan data,such as CT data. This is illustrated in FIG. 5c . The association of thepre-operative plan with the position and orientation of the surgicalinstrument may thus provide grey value data including structures beyondthe surfaces that the surgeon can see while looking at the patient only.The re-slice plane may be generated at a position and orientation of thepre-operative plan that corresponds to a position and orientation of theinstrument relative the patient anatomy. Hence, the re-slice planefollows or tracks the virtual representation of the surgical instrument,which provides for continues access to the pre-operative plan dependenton instrument position and orientation without having to manipulate thesystem.

As indicated above, a plurality of orthogonally arranged display planes56 a, 56 b, 56 c may be fixed relative at least one dimension of thevirtual representation of the surgical instrument 52 or a portion of thepre-operative plan. The origin of the display planes 56 a, 56 b, 56 cmay e.g. be fixed relative the tip, center, and/or longitudinal orinsertion axis of an implant component of the pre-operative plan. Theposition and orientation of the virtual representations of the surgicalinstrument 52 relative the plurality of orthogonally arranged displayplanes 56 a, 56 b, 56 c may be continuously updated. Hence, it is alsocontinuously updated relative the virtual representations of thepre-operative plan in each part of said split window depending on saidtracking data. For example, axial or transverse data of thepre-operative plan may be generated in the second part 51 b of the splitwindow 50 depending on the position and orientation of the virtualrepresentation of the surgical instrument 52 relative the virtualrepresentation of the pre-operative plan. For example, as the virtualrepresentation of the instrument 52 moves along the coronal displayplane 56 c, the virtual representation of the pre-operative plan iscontinuously updated in the transverse display plane 56 a, such as ifthe display plane tracks the virtual representation of the surgicalinstrument 52. For example, the axial or transverse display plane 56 amay be provided at fixed position relative the longitudinal direction ofthe virtual representation of the surgical instrument 52. The fixedposition may be at the center of the virtual representation of thesurgical instrument 52, such as illustrated in FIG. 5c , or at apredetermined distance relative the virtual representation of thesurgical instrument 52, such as illustrated in FIG. 5b . The fixedposition may be user defined, fixed in the system, dependent on the typeof surgical procedure and/or type of implant component. Similarly, asthe virtual representation of the instrument 52 moves along the axial ortransverse display plane 56 a, and/or the sagittal display plane 56 b,position and orientation of the virtual representation of the surgicalinstrument 52 relative the virtual representation of the pre-operativeplan may be continuously updated in the other display planes 56 a, 56 b,56 c.

The position and orientation of the display planes 56 a, 56 b, 56 c maybe based on a planned position and/or a planned orientation of theimplant component of the pre-operative plane relative the patientanatomy data of said pre-operative plan. For example, the axial ortransverse plane 56 a may be oriented in the insertion direction of theimplant component. In other embodiments, the axial or transverse plane56 a is aligned with the axial or transverse plane of the patientanatomy, for example if the axial or transverse plane of the patientanatomy is defined during the pre-operative planning. An indication ofthe orientation of the patient anatomy may be included in thepre-operative plan.

As is illustrated in FIG. 5b , at least one 3D representation isgenerated as the virtual representation of the pre-operative plan in thefirst part 51 a of the split window 50. The 3D representation may beupdated depending on the position of the virtual representation of thesurgical instrument 52. For example, any of the display planes 56 a-56 cmay be cutting planes. The 3D representation may be cut or not displayedon one side of the cutting plane, whereas it is displayed on the otherside. At the same time, a 2D representation as the virtualrepresentation of the pre-operative plan is generated in the second part51 b of the split window 50. The 2D representation may comprise volumeand/or grey value data. Each of the 3D representation and the 2Drepresentation is generated dependent on the tracking data.

Furthermore, grey value data from the patient anatomy data of thepre-operative plan may be generated in at least one of said separateparts 51 a-51 d of the split window 50 depending on the tracking data.As is illustrated in FIG. 5d , grey value data may be generated in anyof the parts 51 a-51 d or the split window 50 relative the position ofthe virtual representation of the surgical instrument 52. Furthermore,at least two of grey value data, volume data, and surface data may becontinuously generated based on the patient anatomy data of thepre-operative plan and in at least one of the separate parts 51 a-51 dof the split window 50 depending on the tracking data. This isillustrated in FIG. 5c , where all types of data are generated relativethe position and orientation the virtual representation of the surgicalinstrument 52, such as the tip thereof. Hence, in some embodiments, thevirtual representation of the surgical instrument 52 relative thevirtual representation of the pre-operative plan may be generated in atleast three orientations in three different parts 51 a-51 d of the splitwindow 52 simultaneously and depending on the tracking data.

In some embodiments, orientation settings for at least one part 51 a-51d of the split window 52 are obtained from the pre-operative plan. Thismay be user defined during the pre-operative planning procedure. Hence,the surgical navigation system may be used by different surgeons havingtheir respective planning modules but yet do not have to define settingsin the CAD module before commencing surgery using the same surgicalnavigation system. The settings may be automatically applied uponimporting the pre-operative plan. Hence, the system is moreuser-friendly and intuitive. Alternatively, the settings are set in auser profile and applied upon logging into the surgical navigationsystem. The orientation setting defines the orientation of at least onevirtual representation of the pre-operative plan in at least one part 51a-51 d of the split window 50.

As is illustrated in FIGS. 5b and 5d , an axial or transverserepresentation of the pre-operative plan is generated in one part of thesplit window 50 and at least one of a coronal representation and asagittal representation of the pre-operative plan is generated in atleast one other part of the split window 50 and depending on thetracking data. The axial or transverse representation of thepre-operative plan may be continuously updated depending on the positionof the virtual representation of the surgical instrument 52, asdescribed above. However, the coronal and/or the sagittal representationmay be static, whereas the position of the virtual representation of thesurgical instrument 52 relative the static representation iscontinuously updated depending on the tracking data. Also, the 3Drepresentation of the pre-operative plan in the first part 51 a may becontinuously updated. Grey value data may be continuously updated in thefirst part 51 a of the split window 50 relative the 3D representation aswell as in the second part 51 b of the split window 50, but not in theother parts 51 c-51 d of the split window. Hence, an objectrepresentation of the patient anatomy and the virtual representation ofthe surgical instrument 52 may be generated in the first part 51 a ofthe split window 50 depending on the tracking data. Also, volumetricrepresentation and/or grey value representation of the patient anatomyand the virtual representation of the surgical instrument 52 may begenerated in the second part 51 b of the split window 50 depending onthe tracking data.

As is illustrated in FIG. 5c , the object representation as well as anvolumetric and/or grey value representation of the patient anatomy dataand the virtual representation of the surgical instrument may begenerated the first part 51 a of the split window 50 depending on thetracking data. The surface representation and the volumetric and/or greyvalue representation are at least partially offset in an axial directionof the patient anatomy. Hence, an offset is provided between thedifferent representations of the pre-operative plan. This represents anaccuracy indication of the system, such as to verify the accuracy of asegmentation process for generating the surface representation. Certainportions of the patient anatomy may have been classified as a particulartype of anatomy, such as bone tissue, whereas it actually is a differenttype of anatomy, such as soft tissue. Presenting both types ofrepresentations allows the surgeon to verify the accuracy of thesegmentation process. The transverse cutting plane in the first part 51a may track or follow the position of the virtual representation of theinstrument 52, such as a tip thereof, but the orientation of thetransverse cutting plane may follow the orientation of the patientanatomy.

FIG. 5e illustrates an embodiment wherein at least one display plane 56e is fixed relative at least one dimension of the virtual representationof the surgical instrument 52. In the illustrated embodiment, it isfixed relative the longitudinal axis, i.e. the insertion direction ofthe surgical instrument. Hence, as the virtual representation of thesurgical instrument 52 rotates, the virtual representation of thepre-operative plan is updated, such as a transverse representation ofthe pre-operative plan, as is illustrated in FIG. 5e . In theillustrated embodiment, only an object representation is generated. Inother embodiments, grey value data is presented at the transversecross-section of the anatomical structure, e.g. such that grey valuedata is generated in the window in the transverse plane. This embodimentmay be combined with any of the other embodiments of the split window50, such as generated in a part 56 a-56 d of the split window.

In still other embodiments the orientation of at least one display planeis fixed relative the orientation of scan data of the pre-operativeplan, such as the orientation of volumetric data, e.g. CT slices ofDICOM files.

In some embodiments, enabling and/or disabling the display planes 56a-56 d is initiated from an actuator, such as a push button, of thetracker 2 a-2 e. Hence, the surgeon can operate the system withoutinteracting with a computer running the surgical navigation system.Furthermore, any of the parts 51 a-51 d of the split window 50 may beenabled or disabled depending on a particular step of the surgicalprocedure, such as insertion of the particular implant component, suchas a cup or stem of a hip replacement procedure. The step of theprocedure may be indicated in a graphical user interface or depending onan identified attachment component.

The method and system for associating the pre-operative plan may be usedtogether with the navigation system presented herein. Hence identitydata may be received from at least one tracker 2 a-2 e of the navigationsystem, wherein the tracker identity data is unique for each tracker 2a-2 e in the navigation system. Position and orientation data of atracker interface attached to the tracker interface of an attachmentcomponent is received. Calibration data defining the position andorientation of a portion of the surgical instrument relative a trackerinterface of the attachment component is obtained. The position andorientation data of the tracker interface is translated into positionand orientation data of the instrument using the identity data and saidcalibration data before generating the virtual representations of thesurgical instrument relative the virtual representation of the patientanatomy. In other embodiments, the method and system for associating thepre-operative plan may be used with other navigation systems wherein theposition and orientation of a surgical instrument is tracked. However,common to these systems is that the virtual representation of thesurgical instrument 52 relative the pre-operative plan corresponds tothe position and orientation of the surgical instrument relative patientduring the operation one the patient anatomy is referenced. Hence, thevirtual representations of the surgical instrument relative multiplevirtual representations of the pre-operative plan are dependent on thetracking data, which provides the position and orientation of thesurgical instrument.

The system for associating a pre-operative plan with position andorientation of a surgical instrument in a surgical navigation systemcomprises a surgical navigation module, such as the surgical navigationsystem 40. The system may be configured to generate a preoperative planwith a virtual representation of patient anatomy and a planned positionand orientation of a surgical object. The navigation system 41 comprisesat least one tracker attachable to an instrument to be tracked, and alocalizer for tracking at least one of position and orientation of saidat least one tracker, such as is disclosed in embodiments herein. The atleast one tracker may comprise the position transmitter and the trackerinterface for attaching the at least one tracker to the instrument. Thenavigation system 41 may be arranged to report tracking data comprisingposition and orientation of the tracker to the surgical navigationmodule. The surgical navigation module may be configured to generatetracked position and orientation of the surgical instrument as virtualrepresentations of the surgical instrument relative virtualrepresentations of pre-operative plan in separate parts of a splitwindow depending on the tracking data. The surgical navigation modulemay comprise the display 4 and the computer 5 comprising a processor andmemory for running software instructions for implementing the method forassociating the pre-operative plan with position and orientation of thesurgical instrument in the surgical navigation system 40.

FIGS. 6a-6d illustrates embodiments of a method for determining at leastone of position and orientation of the instrument using the navigationsystem 41 including at least a first and a second tracker 102 e, 102 b.The method may be implemented e.g. by a computer, such as computer 5.Position and orientation data of the first tracker 102 e, which isattached to a calibration station 101 in a known fixed position andorientation relative a calibration location of the calibration station101, may be generated. Position and orientation data identifyingposition and orientation of the tracker interface of the second tracker102 b may be obtained while the second tracker 102 b is removablyattached to the instrument using the tracker interface of the secondtracker 102 b. The position and orientation of the instrument relativethe second tracker may be determined using the position and orientationdata of the first tracker 102 e, the position and orientation data ofthe tracker interface of the second tracker 102 b, and the known fixedposition and orientation of the calibration location relative theposition and orientation of the first tracker 102 e.

The position and orientation data of the first tracker 102 e maycomprise position and orientation of a tracker interface of the firsttracker 102 e obtained while the tracker interface of the first tracker102 e is attached to the tracker interface of the calibration station101. In other embodiments, the calibration station 101 has an integratedtracker. However, having a tracker interface makes the calibrationstation independent in the navigation system, which makes it moreflexible and the navigation system exchangeable and possible to upgradeto new navigation technology without replacing the calibration station.

The position and orientation data of the second tracker 102 b may bereceived while the second tracker 102 b is attached to the trackerinterface of the attachment component, which in turn is attached to theinstrument. Utilizing an attachment component for attaching the trackermakes the system flexible, and the tracker may be retrofitted to anyinstrument. Hence, the surgeon may continue to use the instrument withwhich he is familiar while benefitting of enhanced information via thenavigation system.

Tracker identity data for at least the second tracker 102 b, whichuniquely identifies the second 102 b tracker in the navigation system 41may be received while obtaining the position and orientation data of thetracker interface of the second tracker 102 b, as will also be furtherdiscussed below. Also, the determined position and orientation of theinstrument relative the second tracker may be stored in a databasetogether with the tracker identity data of the second tracker 102 b, andpreferably with instrument data identifying a specific combination of aninstrument and attachment component. Hence, it is not necessary tocalibrate the specific combination of an instrument and attachmentcomponent every time the tracker is attached to the combination. Ratherthe combination may be identified in the surgical navigation system 40and associated with a particular tracker. The identification may be madeby an operator of the system. Re-calibration is only necessary if theattachment component has been detached from the instrument from aprevious calibration.

A system may be used for calibrating the position and orientation of theinstrument within the navigation system. As discussed above, a firsttracker 101 e is attachable to the calibration station 101 and thesecond tracker 101 b attachable to the attachment component. Thecalibration station 101 has a calibration location for receiving aportion of the instrument. At least one attachment component is providedfor attaching the second tracker 102 b to the instrument. At least thesecond tracker 102 b comprises the tracker interface for attaching thesecond tracker 102 b to a tracker interface of the attachment component.

The first tracker 102 e may comprise a tracker interface for attachingthe first tracker 102 e to a tracker interface of the calibrationstation 101. The tracker interface of the calibration station 101 has afixed position and orientation relative the calibration location.

The tracker interface of the attachment component may be identical tothe tracker interface of the calibration station. This makes the systemaccurate and reliable. If the tracker interfaces comprises ananti-rotational feature, the tracker cannot be accidentally rotated.However, in other embodiments the tracker interface of the calibrationstation 101 comprises an anti-rotational feature, and the second tracker102 b is rotationally attachable relative the tracker interface of theattachment component. Hence, it is easier to orient the tracker 102 brelative the instrument such that it is in a suitable orientationrelative the localizer during surgery.

FIGS. 6a-6d illustrates embodiments of the calibration station 101having a tracker interface 124 identical to the tracker interface 44 ofthe attachment components, as discussed above. Hence, a tracker 102 e isattachable to the calibration station in a fixed position andorientation relative the calibration station.

FIGS. 6a-6d also illustrates embodiments of the method for determiningat least one of position and orientation of the instrument, such asdetermining the position of a particular attachment component 110 andinstrument 103 b combination. The method may be implemented by the CADmodule 42 to transform position and orientation of a tracker to positionand orientation of at least a portion of the instrument 103 b. Thecalibration station 101 is associated with a known calibration location108 for an end effector of a surgical instrument, such as a tip of thesurgical instrument, a plane of the surgical instrument, a center ofrotation of the instrument, and/or a combination thereof.

The tracker interface 124 of the calibration station 101 has a fixedpredetermined position and orientation relative the calibration location108. The position and orientation of the calibration location relativethe position and orientation of the tracker interface 124 of thecalibration station 101 is known to the surgical navigation system 30,such as to the CAD module 42. The tracker interface 124 of thecalibration station 101 may be defined as the origin for thecalibration, relative which other components positions and orientationsare reported.

Calibrating the position and orientation of the instrument 103 b may bemade using two trackers 102 b, 102 c. Each tracker 102 b, 102 ccomprises a tracker interface, as has been discussed above. Hence, eachtracker 102 b, 102 c comprises a trackable surface within the navigationsystem 41. The instrument interface of the attachment component 110 isattachable to the surgical instrument 103 b. A first tracker 102 e isattachable to the tracker interface 124 of the calibration station 101.A second tracker 102 b is attachable to the tracker interface of theattachment component 110.

FIG. 6a illustrates the system uncalibrated, wherein the first andsecond trackers 102 e, 102 b are in a first coordinate system x₁, y₁, z₁known to the navigation system; the calibration station is in a secondcoordinate system x₂, y₂, z₂; and the surgical instrument is in a thirdcoordinate system x₃, y₃, z₃. The position and orientation of the firsttracker 102 e or the second tracker 102 b may be defined as origin forthe calibration. The following embodiments are described with regard tothe first tracker 102 e, i.e. its tracker interface, as providing theorigin. However, the second tracker 102 b may be defined as origin forthe calibration in other embodiments. Since the origin is predefined,the navigation system only needs to report the position and orientationof the tracker interface of the second tracker 102 b relative origin.Identifying the position and orientation of the first tracker 102 eidentifies the origin. The position and orientation of the first trackerattached to a calibration station in a known fixed position andorientation relative the calibration location 108 of the calibrationstation 101 does not have to be reported to the CAD module, which mayset this value to a default value. The relative position and orientationbetween the first tracker 1020 e and the relative position andorientation between the first tracker, i.e. the origin for calibration,and the tracker interface of the second tracker 102 b may be obtainedfrom the navigation system. Data of the relative position andorientation may be obtained in the CAD module. The position andorientation of the instrument is determined using the relative positionand orientation between the first tracker, i.e. origin, and the trackerinterface of the second tracker 102 b, and the known fixed position andorientation of the calibration location relative the position andorientation of the first tracker, i.e. relative origin. These may becalculated based on the values of the known origin, the known positionand orientation of the calibration location relative the position andorientation of the first tracker, i.e. relative origin, and the obtainedrelative position and orientation between the first tracker, i.e.origin, and the tracker interface of the second tracker 102 b.

Returning to FIG. 6a , the first, second and third coordinate systemsare uncalibrated. The first coordinate system is the coordinate systemof the navigation system. In a first step illustrated in FIGS. 6a-6b ,the second coordinate system x₂, y₂, z₂ is aligned or coordinated withthe first coordinate system x₁, y₁, z₁ by attaching the first tracker102 e to the tracker interface of the calibration station 101. Thisidentifies the origin for the calibration, wherein the position of thetracker interface 124 of the calibration station 101 is known in thecoordinate system x₁, y₁, z₁ of the navigation system 30, as isillustrated in FIG. 6b . The tracker interface 124 of the calibrationstation 101 is now located at the origin for the calibration, identifiedby the first tracker 102 e. Also, the third coordinate system x₃, y₃, z₃is aligned or coordinated with the first coordinate system x₁, y₁, z₁ byattaching the second tracker 102 b to the tracker interface of theattachment component 110 having its instrument interface attachedrelative the surgical instrument 103 b. In some embodiments, theinstrument interface is fixed to the instrument in two dimensions, suchas the x and z dimensions, and has a predetermined stop position in thethird dimension, such as the y dimension. Such predetermined stopposition may be a stop member of the instrument and/or instrumentinterface such that the attachment component cannot move any further inone direction along the third dimension. For example, the attachmentcomponent may be attached to a rotatable shaft, such as the shaft of areamer or planar, such that it may move along the shaft but not betilted relative the shaft. Calibration occurs when the attachmentcomponent is at the stop member, such that the surgeon always can returnto the calibrated position of the attachment component relative theinstrument. Attaching the attachment component 110 to the surgicalinstrument 103 b is not illustrated. Hence, the position and orientationof the tracker interface of the attachment component 110 is known in thecoordinate system x₁, y₁, z₁ of the navigation system 30, as isillustrated in FIG. 6b . However, the position and orientation of theend-effector of the surgical instrument in the coordinate system x₁, y₁,z₁ of the navigation system 30, i.e. relative origin, is still unknown.

FIGS. 6c-6d illustrates coordinating or registering the position andorientation of the surgical instrument 103 b in the coordinate systemx₁, y₁, z₁ of the navigation system 30. This is done by positioning theend effector of the instrument 103 b at the calibration location 108.The end effector may be the portion of the instrument that is to betracked in the CAD module 42. The end effector may be a surface of theinstrument, such as a surface of a reamer, a tip of a drill or otherinstrument etc. It may also be a center of rotation of an instrument,such as the center of a reamer or a planar. In the illustratedembodiment, the end effector is the center of rotation of a reamer. Asis illustrated in FIG. 6c , the end effector of the instrument ispositioned at the calibration location 108. Next, the position andorientation of the second tracker 102 b relative the position andorientation of the first tracker 102 e, such as the position andorientation of their tracker interfaces, are registered by thenavigation system. In some embodiments, only the position andorientation of the tracker interface of the second tracker 102 brelative the position and orientation of the tracker interface of thefirst tracker 102 e is reported. This is sufficient when the origin forcalibration is predefined as the location of the tracker interface ofthe first tracker 102 e. The position and orientation of the trackerinterface of the second tracker 102 b may be obtained by the CAD module42 from the navigation system. In other embodiments, the positions andorientations of the tracker interface of the first as well as of thesecond tracker are obtained.

Since the position and orientation of the calibration location 108relative the first tracker 102 e, i.e. relative the calibration origin,is known, the position and orientation of the second tracker 102 brelative the end-effector of the surgical instrument 103 b can bedetermined and stored, such as in a transformation table or database.This may also be stored together with tracker identity and instrumentidentity, for example if multiple tools are used at the same time, or ifthe tracker is connected to different instruments during various stepsof the surgical procedure. Hence, the coordinate systems arecoordinated, and the position and orientation of the end-effector of thesurgical instrument 103 b may be continuously determined by tracking andtranslating the position and orientation of the second tracker 102 b,i.e. the position and orientation of the tracker interface thereof.

The calibration method may be used for any instrument and anyreplacement system. The system may be used with only two trackers inorder to track position and orientation of any instrument. Hence, thesystem is extremely flexible and may easily be adapted to newreplacement systems. Furthermore, an intermediate attachment interfacethat has a predefined shape means that the surgical navigation system 31can be replaced by new navigation technology. The navigation systemsimply needs to report the position of the tracker interface relative anorigin of the system, such as for calibration.

As discussed above, to calibrate the position and orientation of thesurgical instrument 103 b in the first coordinate system, theend-effector is positioned at the calibration location 108. Thecalibration location may be a recess or a protrusion in or at a surfaceof the calibration station 101, such that it has a substantially fixedposition at one point and/or in one plane, e.g. the x₁-z₁ plane,illustrated in FIGS. 6c -6 d.

In some embodiments, the position of the tracker interface of the secondtracker 102 b may be registered while moving the surgical instrument,and thus the attachment component and the second tracker 102 b attachedthereto. The attached components may be moved in at least a secondplane, such as the x₁-y₁ plane and/or y₁-z₁ plane, and while theend-effector is positioned at the calibration location 108, i.e. has arelatively fixed position in one point or one plane, such as the x₁-z₁plane. Multiple positions and orientations of the tracker interface ofthe second tracker 102 b are registered while moving in the secondplane. At the same time, the position and orientation of the firsttracker 102 e is registered. Based on these registered positions andorientations, the position and orientation of the center of rotation ofthe second tracker 102 b, and thus the center of rotation of theend-effector, may be calculated. Also, the position and orientation ofthe axis of the surgical instrument 103 b relative the tracker interfaceof the second tracker 102 b may be calculated.

In FIG. 6d , the surgical object 93 is shown in a single position forillustrative purposes. As an alternative calibration method, thesurgical instrument may be positioned perpendicularly to a calibrationplane of the calibration station 101 while the position and orientationof the tracker interface of the second tracker 102 b is registered. Thecalibration plane has a fixed orientation relative the tracker interfaceof the calibration station 101, i.e. relative calibration origin. Hence,the position and orientation of the axis of the surgical instrument 103b within the first coordinate system may be calculated using thecalibration plane and calibration location 108. The calibration planemay be the top surface 109 of the calibration station, as is illustratedin FIG. 6d . The instrument may be attached to a calibration supportthat has a shape that is complementary to the shape of surfaces at thecalibration location, such as part-spherical component with legsextending along the calibration plane and that supports the instrumentduring calibration and keeps it stable in the plane. Three such legs maybe sufficient for fixed angular relationship between the longitudinalaxis of the instrument and the calibration plane during the calibrationprocess.

The navigation system may comprise at least one tracker attachable to aninstrument to be tracked and a localizer for tracking at least one ofposition and orientation of said at least one tracker. The at least onetracker may comprise a position transmitter and a tracker interface forattaching the at least one tracker to the instrument, as has beendiscussed above. Position and orientation of position transmitter may beused by the navigation system to obtain position and orientation of thetracker interface of the tracker. The positional and orientationrelationship between the position transmitter and the tracker interfaceis predetermined and known to the navigation system, which may beconfigured to report the position and orientation of the tracker withinthe navigation system.

Embodiments comprise a method for tracking position and orientation ofthe instrument using the navigation system 41. The method may beimplemented in the surgical navigation system 41, such as a by acomputer running the CAD module 42. As is discussed above, thenavigation system may include a plurality of trackers 2 a-2 e and alocalizer for identifying the position and orientation of the tracker.Each tracker may have a unique identity in the navigation system, suchas an identification no. The tracker identity data is unique for eachtracker in the navigation system. Identity data, such as theidentification no. may be reported by the tracker 2 a-2 e, such as usinga wireless transmitter, e.g. using wireless radio technology, such asWiFi or Bluetooth technology. The identity is reported to the navigationsystem. Furthermore, the position and orientation of the trackerinterface of the tracker 2 a-2 e for with identity no. has been receivedmay be determined by the navigation system. Sending the identity datafrom the tracker may be triggered, such as initiated by a useractivating an actuator. The navigation system may determine the positionand orientation of the tracker upon receiving the identity data.According to the method, identity data from at least one tracker of thenavigation system is received. Also, position and orientation data ofthe tracker interface being attached to the tracker interface of theattachment component is obtained. The identity data and the relatedposition an orientation data of the reporting tracker may be used totranslate the position and orientation data of the tracker interface ofthe reporting tracker into position and orientation data of theinstrument. The identity data may be used to query a database toobtaining calibration data defining the position and orientation of aportion of the instrument, such as discussed above. Then, the positionand orientation of the instrument may be determined based on thecalibration data. The calibration data may be obtained as discussedabove. Similarly, the method may comprise attaching the tracker to theattachment component, and the attachment component to the instrument, ashas been discussed above.

FIG. 7 illustrates an embodiment of a tracker 202 according toembodiments of the invention. The tracker 202 has a position transmitterarranged in a fixed and predetermined position relative the trackerinterface 213. The position transmitter may comprise as a plurality ofactive and/or passive markers arranged in a predetermined relationshipand/or having predetermined shapes. In this embodiment, the positiontransmitter comprises an active position transmitter, which comprises aplurality of LEDs 219 a-219 f arranged in a known pattern relative thetracker interface 213 of the tracker 202. The markers have a knownposition and orientation relative the origin of the coordinate system ofthe tracker 202, which is located at its tracker interface 213 accordingto embodiments described herein. The localizer may in this embodimentcomprise a camera to capture the position of the position transmitter,such as light transmitted by the LEDs 219 a-219 f, which a processorthereof may utilize to determine the position and orientation of the ofthe tracker interface 213. Transmission of position information may betriggered by actuators integrated in the housing of the tracker (notillustrated). A system for obtaining the position based on activemarkers is e.g. disclosed in WO91/16598, which is incorporated herein byreference for all purposes. Another example is disclosed in disclosed inU.S. Pat. No. 5,440,392, which is incorporated herein by reference forall purposes. Another embodiment of an optical navigation system isdisclosed in U.S. Pat. No. 6,166,809, which is incorporated herein byreference for all purposes, with which both position and orientation maybe obtained. Embodiments of the present invention may also be used withinertial navigation systems, wherein sensors such as accelerometers andgyros are arranged in a known position and orientation relative thetracker interface 213 of the tracker 202. As is illustrated in FIG. 7and according to embodiments of the present invention, the coordinatesystem is located at the tracker interface 213, e.g. such that the yaxis is extending along the longitudinal axis of the tracker interface213, and is located at the center of the tracker interface 213. The xand z axes are extending parallel to a plane formed by the tip or freeend of the tracker interface 213. The markers have a known position andorientation relative the origin of the coordinate system of the tracker202, which is located at its tracker interface 213. This means anythingcan be aligned and tracked relative the tracker interface 213.

FIGS. 8a-8c, and 11a-11b illustrate front, side, and perspective views,respectively, of an embodiment of the tracker interface of theattachment component. As discussed above, the tracker interface of theattachment component may comprise a protrusion 226 extending from a base227. The base 227 has a larger cross-sectional diameter than theprotrusion 226 as measured perpendicularly relative the longitudinalaxis of the tracker interface. This means that the base 227 has a topsurface 240 (not illustrated in FIG. 8c ) facing the towards the trackerinterface of the tracker. The protrusion 226 is in this embodimentsemi-circular with a radially facing non-circular surface 241. Thenon-circular surface 241 may be a generally flat or planar surfaceextending in a plane that is perpendicular to the top surface 240 of thebase 227. Furthermore, the tracker interface comprises a locking feature242, for locking engagement of the tracker interface to a trackedsurface of the tracker, such as the tip of the tracker interface 213 ofthe tracker 202. In this embodiment, the locking feature 242 is asemi-circular recess provided in the non-circular surface 241. Thelocking feature 242 may extend perpendicularly relative the longitudinalaxis of the tracker interface and parallel to the top surface 240 of thebase 227. In this embodiment, the locking feature 242 only extendspartially around the circumference of the protrusion 226. In otherembodiments, the locking feature 242 extends around the entirecircumference of the protrusion 226, which may improve stability andthus accuracy of tracking of the attachment component.

FIGS. 9a-9c illustrate attaching the tracker interface 225 of thetracker to the tracker interface of the attachment component. In thisembodiment, the tracker interface 225 of the tracker comprises a chuck.The chuck comprises a boss 230 with a generally flat or planar endsurface 231, which may be part of or form the tip of the tracker, and arecess (not illustrated). The end surface 231 extends perpendicularlyrelative the longitudinal axis of the recess of the tracker interface225. Furthermore, the chuck comprises a locking element that comprisesan eccentric rod 234 connected to a level arm or actuator 235. Theeccentric rod 234 is arranged perpendicularly relative the longitudinalaxis of the recess of the tracker interface 225. The level arm isarranged to swivel the eccentric rod 234, which is rotatably arranged inthe tracker interface 225 of the tracker.

As is illustrated in FIG. 9a , the tracker interface 225, i.e. therecess, of the tracker 202 is configured to fit over the protrusion 226of the tracker interface of the attachment component. The recess andprotrusion may fit in a location fit. The semi-circular surface of theprotrusion 226 has a shape that substantially corresponds to a shape ofan inner radially facing surface extending in the longitudinal directionof the tracker interface 225 of the tracker. The semi-circular surfacesare arranged and sized to abut each other, at least in a locked positionof the tracker interfaces.

As is illustrated in FIG. 9b , when the tracker interface 225 of thetracker is fully seated, it fits over the protrusion 226 of the trackerinterface of the attachment component, as is illustrated with phantomlines. Also, the end surface 231 of the tracker interface 225 of thetracker may abut the top surface 240 of the tracker interface of theattachment component. Also the locking feature 242 faces the lockingelement. Before being locked, the locking element is positioned suchthat the maximum distance between the eccentric rod and thesemi-circular surface of the recess is slightly larger than the maximumdiameter of the protrusion 226 measured at the longitudinal axis of thenon-circular surface 241 perpendicularly to the semi-circular surface ofthe protrusion 226. In this position, the tracker interface 225 of thetracker is aligned with the tracker interface of the attachmentcomponent, as is illustrated with the unlocked pad lock symbol.

As is illustrated with a locked pad lock symbol in FIG. 9c , the trackerinterfaces may be locked to each other when the lever arm 235 is pushedor swivel to a locked position, such that the eccentric rod 234 ispositioned within the locking feature 242. Hence, the locking element ispositioned such that the maximum distance between the eccentric rod andthe semi-circular surface of the recess is smaller than the maximumdiameter of the protrusion 226 measured at the longitudinal axis of thenon-circular surface 241 perpendicularly to the semi-circular surface ofthe protrusion 226. Furthermore, the tracker interface of the trackermay be pushed towards the tracker interface of the attachment componentin the locked position, such as by the eccentric rod 234 engaging thelocking feature 242. This may e.g. be provided by the eccentric rodengaging at least a portion of the semi-circular recess provided in thenon-circular surface 241, such as at an upper or lower surface thereof.Hence, the tracker interfaces are locked in a position such that thetracked surface of the tracker abuts a tracked surface of the attachmentcomponent. Thereby the tracker interfaces share a common origin, as isillustrated with the y/z axes (x axis extending into the plane of FIG.9c ). Hence, tracking position and orientation of the tracker interfaceof the tracker also tracks the attachment component when locked to eachother.

Furthermore, the tracker interface 213 of the tracker 202 is acalibrated tracker interface, wherein its exact position and orientationin the navigation system is predefined and known and does not need to becalibrated. The position and orientation within the navigation systemmay be pre-calibrated during manufacturing, such as against a mastercalibration tool, e.g. including an interface corresponding to thetracker interface of the attachment component, which is mounted in afixed relationship relative calibration markers. Reading the positionand orientation of the position transmitter relative the coordinatesystem of the master tool calibration markers may pre-calibrate orcharacterize the tracker interface of the tracker to the master tool.This may be done prior to delivery of the navigation system.

The calibration station 101 described with regard to FIGS. 6a-6d is acalibration object that may be stationary, i.e. it is not attached tothe instrument. As such, the calibration object may have a platform,which is configured to be positioned stably on a surface during thecalibration procedure, e.g. such that the instrument can be positionedat a predefined position relative the calibration location. Thisprovides for a simple and stable positioning of the instrument relativethe calibration station. The instrument does not need to be fastened tothe stationary calibration station during the calibration procedure.However, the navigation system may only include a single positiontracker 6, such as a single camera or a receiver of accelerometer andgyro data from the trackers. For example, the calibration may be doneshortly before a surgery commences in order to assure accuracy of thesystem. That means that the position tracker 6 is arranged such that thepatient will be located within the operational range of the positiontracker 6, which may cover a portion of the operating table and arelatively small volume surrounding the operating table. Duringcalibration, the trackers also need to be within the operational rangeof the position tracker 6. This has the consequence that it may incertain situations and/or for certain navigation systems be inconvenientor impractical to arrange the calibration station 101 in the operationalrange of the position tracker 6, which is arranged in an optimalposition for surgery but not necessarily for calibration. This may e.g.be the case for optical navigation systems, but not for inertialnavigations systems, which are not limited by a field of view of acamera.

FIGS. 10a-10e and 11a-11c disclose embodiments of calibration objects101 a, 101 b, 101 c, 101 d that are mobile calibration stations, as isenvisaged within the scope of the calibration station as discussed withregard to FIG. 4, i.e. for calibrating location, such as position and/ororientation of the instrument 103 b, 14 a within a navigation system.The mobile calibration station 101 a-101 d may comprise elements asdisclosed with regard to FIGS. 6a-6d , and the same features are denotedwith the same reference numerals. Hence, the mobile calibration object101 a-101 d can be used for calibrating location of any of theinstruments 103 b illustrated in FIG. 6a-6d , which may comprise a atleast a portion of a reamer instrument, e.g. a reamer shaft asillustrated in FIGS. 10a, and 10c-10e , and the instrument 14 a, whichmay comprise a cup inserter, as illustrated in FIG. 10b . Theinstruments illustrated in FIGS. 10a-10e and 11a-11c are only examples,other examples as disclosed herein as well as other instruments orportions thereof may be subject of the embodiments disclosed herein forcalibrating their location within the navigation system, such as aninstrument positioning a stem of a hip implant.

As the previous embodiments discussed above, the embodiments of FIGS.10a-10e and 11a-11c may be used together with a first tracker 102 e, anda second tracker 102 b. The embodiments of the tracker interface forattaching a tracker 102 e of the navigation system to the mobilecalibration objects 101 a-101 d may correspond to the tracker interface124 discussed above, such as with regard to FIGS. 6a-6d and will not bediscussed again with regard to FIGS. 10a-10e and 11a-11c except withregard to alternative embodiments. Similarly, the attachment components10 a-10 d and 110 discussed above may equally be used together with theembodiments of FIGS. 10a-10e and 11a-11c and will not be discussed againwith regard to FIGS. 10a-10e and 11a-11c except with regard toalternative embodiments.

FIGS. 10a-10e and 11a-11c illustrate embodiments of calibration objects101 a-101 d that may be mobile. As is illustrated in FIGS. 11a-11c , thecalibration object 101 a, 101 b comprises a calibration body 111 a, 111b having a calibration location 108 a, 108 b for receiving a portion ofthe instrument 013 b in a predefined position, in the same way as theembodiments of FIGS. 6a-6d . The tracker interface has a predeterminedlocation relative the calibration location 108 a, 108 b. The trackerinterface may comprise the protrusion 226 extending from the base 227,the top surface 240, the radially facing non-circular surface 241,and/or the locking feature 242, which may be a semi-circular recessprovided in the non-circular surface 241, as has been discussed above.Furthermore, the tracker interface of the calibration object 101 a-101 dmay comprise the origin for the calibration. The origin may have apredetermined location, such as fixed position and orientation, relativethe calibration location 108 a, 108 b.

As is illustrated in FIG. 11a , the embodiments of FIG. 10a-10d, 11a-11b, as well as the embodiments of FIGS. 6a-6d , the calibration location108 a, 108 b may comprise an instrument attachment member configured forreleasable fastening of the calibration object 101 a-101 d to aninstrument, such as in a predetermined position and/or orientation.Hence, the calibration body 111 a, 111 b may be releasably fastened inthe rotational and/or axial direction relative the instrument 14 a, 103a. Hence, the tracker 102 b, when attached to the calibration object 101a-101 d, is also fixed in the rotational and/or axial direction relativethe instrument 14 a, 103 a. Surgical instruments, such as instrument 14a, 103 a, may have an attachment interface in order to switch betweendifferent sizes of end effectors and/or for releasable fastening of animplant. The instrument attachment member may be configured forreleasable attachment to the attachment interface of any such surgicalinstrument. For example, the instrument attachment member of theembodiment of FIG. 11a comprises pins forming a cross, that hooks of theinstrument attachment interface may engage. The size of the pinscorresponds to the size of the hooks. The pins may be formed in thecenter of a ring shaped body, which comprises the tracker interfaceattached on its surface projecting outwardly relative the center. Thepins provide for axial and rotational attachment of the instrument tothe calibration location 108 a, 108 b. Similarly, the embodiment of FIG.11b-11c comprises a surface with at least one recesses and/or protrusionforming the instrument attachment member. The embodiment of FIG. 11ccomprises two recesses. Each recess may comprise a snap fit attachmentinterface, e.g. comprising protrusions extending in the radial directionof the recess. Such a snap fit attachment interface may be fixed in theaxial direction, but may not necessarily be fixed in the rotationdirection, such as if a position of the tool is to be guided but not anorientation of the tool. The recess of the surface may alternatively oradditionally comprise a press-fit and/or friction fit connection. Hence,the calibration object 101 a-101 d, such as its instrument attachmentmember, may comprise at least one surface that has a shape that iscomplementary to a shape of a surface of the instrument attachmentinterface.

In the embodiment of FIG. 11a , the calibration body 111 comprises acircular member, such as ring shaped member, with the instrumentattachment member in the center. Such a calibration body may be usefulfor a tool such as a reamer.

In the embodiment of FIGS. 11b-11c , the calibration body 111 comprisesa part-spherical member, such as half-spherical, with the attachmentmember at a substantially flat surface of the part-spherical member.Such a calibration body may be useful for a tool such as a cup inserter.

Returning to FIGS. 10a-10e , the calibration object 101 a-101 d providesfor a more flexible calibration method. The calibration object 101 a-101d may be temporarily fixedly attached or fastened to the surgicalinstrument 14 a, 103 a, and the trackers 102 a, 102 e attached to theirrespective tracker interfaces. Then, the operator can grab theinstrument 14 a, 103 a with a single hand, move the entire unitincluding the attachment component 110, the calibration object 101 a-101d, and the trackers 102 a, 102 e, and hold the unit within theoperational range of the position tracker 6. Hence, the operator canprepare the instrument 14 a, 103 a for calibration at one location, andthan only be within the operational range of the position tracker 6 fora short period of time. Furthermore, this means that one operator mayprepare the navigation system for surgery while another operatorprepares the instrument(s) for calibration. Calibration may convenientlybe carried out also when the position tracker 6 is positioned forsurgery relative an operating table. Hence, the calibration process aswell as the entire navigation system is more flexible, which is usefulfor any navigation system, but particularly for navigation systems withmore limited operational range, such as optical navigation systems.

As is illustrated in FIG. 10a , the system may be calibrated with thesurgical tool, such as a drilling machine, attached to the surgicalinstrument 103 b. Alternatively, the system may be calibrated with thesurgical tool detached from the surgical instrument, such as illustratedin FIG. 10 c.

FIGS. 10d-10e illustrate embodiments wherein the calibration object 101c, 101 d is attached to a tool-engaging end of the instrument 103 b,such as for engaging a chuck of a surgical tool, e.g. a chuck of adrilling machine. The tool-engaging end of the instrument 103 b may havean antirational engagement member for antirational engagement with thesurgical tool. The calibration object 101 c, 101 b may be configuredwith complementary surfaces corresponding to the chuck of the surgicaltool, such that the calibration object 101 c, 101 d may be attached at apredetermined location relative an end-effector end of the instrument103 b. Hence, the location of the calibration object 101 c, 101 d, whentemporarily attached to the tool-engaging end of the instrument 102 b,relative the location of the end-effector end is predetermined andknown. Knowing the shape of the end-effector, the relative positionrelative to the end-effector, when attached to the end-effector end, mayalso predetermined and known. This information may be stored in adatabase.

The calibration object 101 c, 101 d may have a body that comprises thetracker interface for attachment to the tracker and an instrumentattachment interface for engagement to the tool-engaging end of theinstrument 103 b. The instrument attachment interface has a fixedpredetermined location relative the end-effector end of the instrument103 b. Hence, by calibrating against the tool-engaging end, the locationof the end-effector end of the instrument 103 b may be determined andtracked using the tracker 102 b attached to the attachment components 10a-10 d and 110 as discussed above.

As is illustrated in FIGS. 10d, 10e , the tracker interface of thecalibration body 101 c, 101 d can be arranged at an arbitrary positionrelative the instrument 103 b. In the embodiment of FIG. 10d , thetracker interface is arranged parallel to the longitudinal axis of theinstrument 103 b. In the embodiment of FIG. 10e , the tracker interfaceis arranged non-parallel to the longitudinal axis of the instrument 103b, such as substantially perpendicular to the longitudinal axis of theinstrument 103 b. Hence, the orientation of the tracker interfacesrelative the instrument 103 b may be optimized for visibility to theposition tracker 6, wherein the calibration process is optimized.

The calibration object 101 a, 101 b may comprise the body 111 a, 111 b,which may comprises at least one of the calibration location 108 a, 108b and the tracker interface. The calibration location 108 a, 108 b maybe integrally formed with the body. Additionally or alternatively, thetracker interface of the calibration body may be integrally formed withthe calibration body 111 a, 111 b. Hence, the calibration location 108a, 108 b and/or the tracker interface of the calibration object 101 a,101 b, as well as the calibration body 111 a, 111 b, may be formed as asingle unit, such as in a single material. Alternatively, the trackerinterface is detachably attached to the calibration body at apredetermined location relative the calibration location 108 a, 108 b inthe same way as the tracker interface 13 d relative the body 11 d ofFIG. 2e . Hence, the tracker interface may be detachably attached to thecalibration body 111 a, 111 b at a predetermined location relative thecalibration location 108 a, 108 b.

As described above, the system for calibrating position and orientationof an instrument within a navigation system may comprise a calibrationobject, such as a stationary and/or mobile calibration body, wherein thetracker interface of the calibration object is a first trackerinterface, the attachment component comprises a tracker interface, whichis a second tracker interface. The navigation system comprises the firsttracker 102 e attachable to the first tracker interface and a secondtracker 102 b attachable to the second tracker interface. The firsttracker interface and the second tracker interface may be identical.

As will be apparent, the features and attributes of the specificembodiments disclosed above may be combined in different ways to formadditional embodiments, all of which fall within the scope of thepresent disclosure.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or states are included or are to beperformed in any particular embodiment.

Any process descriptions, elements, or blocks in the flow diagramsdescribed herein and/or depicted in the attached figures should beunderstood as potentially representing modules, segments, or portions ofcode which include one or more executable instructions for implementingspecific logical functions or steps in the process. Alternateimplementations are included within the scope of the embodimentsdescribed herein in which elements or functions may be deleted, executedout of order from that shown or discussed, including substantiallyconcurrently or in reverse order, depending on the functionalityinvolved, as would be understood by those skilled in the art.

The processes and systems described herein may be performed on orencompass various types of hardware, such as computer systems. In someembodiments, computer, display, and/or input device, may each beseparate computer systems, applications, or processes or may run as partof the same computer systems, applications, or processes—or one of moremay be combined to run as part of one application or process—and/or eachor one or more may be part of or run on a computer system. A computersystem may include a bus or other communication mechanism forcommunicating information, and a processor coupled with the bus forprocessing information. The computer systems may have a main memory,such as a random access memory or other dynamic storage device, coupledto the bus. The main memory may be used to store instructions andtemporary variables. The computer systems may also include a read-onlymemory or other static storage device coupled to the bus for storingstatic information and instructions. The computer systems may also becoupled to a display, such as a CRT or LCD monitor. Input devices mayalso be coupled to the computer system. These input devices may includea mouse, a trackball, or cursor direction keys.

Each computer system may be implemented using one or more physicalcomputers or computer systems or portions thereof. The instructionsexecuted by the computer system may also be read in from acomputer-readable medium. The computer-readable medium may be a CD, DVD,optical or magnetic disk, laserdisc, carrier wave, or any other mediumthat is readable by the computer system. In some embodiments, hardwiredcircuitry may be used in place of or in combination with softwareinstructions executed by the processor. Communication among modules,systems, devices, and elements may be over a direct or a switchedconnection, and wired or wireless networks or connections, via directlyconnected wires, or any other appropriate communication mechanism. Thecommunication among modules, systems, devices, and elements may includehandshaking, notifications, coordination, encapsulation, encryption,headers, such as routing or error detecting headers, or any otherappropriate communication protocol or attribute. Communication may alsobe messages related to HTTP, HTTPS, FTP, TCP, IP, ebMS OASIS/ebXML,secure sockets, VPN, encrypted or unencrypted pipes, MIME, SMTP, MIMEMultipart/Related Content-type, SQL, etc.

Any appropriate 3D graphics processing may be used for displaying orrendering including processing based on OpenGL, Direct3D, Java 3D, etc.Whole, partial, or modified 3D graphics packages may also be used, suchpackages including 3DS Max, SolidWorks, Maya, Form Z, Cybermotion 3D, orany others. In some embodiments, various parts of the needed renderingmay occur on traditional or specialized graphics hardware. The renderingmay also occur on the general CPU, on programmable hardware, on aseparate processor, be distributed over multiple processors, overmultiple dedicated graphics cards, or using any other appropriatecombination of hardware or technique.

As will be apparent, the features and attributes of the specificembodiments disclosed above may be combined in different ways to formadditional embodiments, all of which fall within the scope of thepresent disclosure.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or states are included or are to beperformed in any particular embodiment.

Any process descriptions, elements, or blocks in the flow diagramsdescribed herein and/or depicted in the attached figures should beunderstood as potentially representing modules, segments, or portions ofcode which include one or more executable instructions for implementingspecific logical functions or steps in the process. Alternateimplementations are included within the scope of the embodimentsdescribed herein in which elements or functions may be deleted, executedout of order from that shown or discussed, including substantiallyconcurrently or in reverse order, depending on the functionalityinvolved, as would be understood by those skilled in the art.

All of the methods and processes described above may be embodied in, andfully automated via, software code modules executed by one or moregeneral purpose computers or processors, such as those computer systemsdescribed above. The code modules may be stored in any type ofcomputer-readable medium or other computer storage device. Some or allof the methods may alternatively be embodied in specialized computerhardware.

It should be emphasized that many variations and modifications may bemade to the above-described embodiments, the elements of which are to beunderstood as being among other acceptable examples. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the following claims.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are equally possible within the scope of the invention.Different method steps than those described above may be provided withinthe scope of the invention. The different features and steps of theinvention may be combined in other combinations than those described.The scope of the invention is only limited by the appended patentclaims.

1. An attachment component for attaching a tracker of a navigationsystem to an instrument, said attachment component comprising: a body,an instrument interface attached to the body and configured fordetachable attachment of the attachment component to an instrument orimplant; a tracker interface attached to the body and having a fixedpre-defined shape for engagement with a calibrated tracker interface ofthe tracker, wherein the instrument interface has in an arbitraryun-calibrated position relative the tracker interface.
 2. The attachmentcomponent according to claim 1, wherein at least the body and theinstrument interface are formed as an integral unit, and wherein theinstrument interface comprises at least one recess for engagement withthe surgical instrument, or the instrument interface comprises at leastone clamp for clamping the attachment component to surgical instrument.3. The attachment component of claim 1, wherein at least one of positionand orientation of the tracker interface relative the position andorientation of the instrument interface is adjustable.
 4. The attachmentcomponent according to claim 1, wherein the fixed predefined shape ofthe tracker interface comprises an anti-rotational feature, which isnon-circular and non-spherical, for anti-rotational engagement to asurface of the tracker interface of the tracker having a complementaryshape.
 5. The attachment component according to claim 1, wherein thetracker interface comprises a locking feature, for locking engagement ofthe tracker interface to a tracked surface of the tracker.
 6. A set ofattachment components, comprising at least two attachment componentsaccording to claim 1, wherein the instrument interface of at least twoof said attachment components have different geometrical shapes, andwherein the tracker interface of at least two of said attachmentcomponents have identical geometrical shapes.
 7. The set of attachmentcomponents according to claim 6, wherein each attachment componentfurther comprises an electronically readable identifier configured toidentify at least one of instrument brand and instrument type of thesurgical instrument, for which the instrument interface of theattachment component is configured.
 8. The set of attachment componentsaccording to claim 7, wherein said electronically readable identifiercomprises a transmitter for wirelessly transmitting an identificationcode unique for said at least one of instrument brand and instrumenttype of the surgical instrument, for which the instrument interface ofthe attachment component is configured.
 9. A device, comprising, incombination, an attachment component according to claim 1 and acalibration station having a tracker interface identical to the trackerinterface of the attachment component, wherein the calibration stationis associated with a known calibration location for an end effector ofan instrument, wherein the tracker interface of the calibration stationhas a fixed position relative the calibration location.
 10. The deviceaccording to claim 9, further comprising, in combination, an instrument,and at least two trackers of a navigation system, wherein each trackercomprises a tracker interface with a trackable surface having apre-defined shape and location, wherein the instrument interface of theattachment component is attachable to the instrument, a first tracker isattachable to the tracker interface of the attachment component, and asecond tracker is attachable to the tracker interface of the calibrationstation.
 11. A navigation system comprising; at least one trackerattachable to an instrument to be tracked; a localizer for tracking atleast one of position and orientation of said at least one tracker;wherein the at least one tracker comprises a position transmitter and atracker interface for attaching the at least one tracker to saidinstrument; and the navigation system is arranged to report position andorientation of the tracker interface of the tracker.
 12. The navigationsystem according to claim 11, wherein the navigation system is asurgical navigation system and the instrument is a surgical instrument.13. A method for tracking position and orientation of an instrumentusing a navigation system including a plurality of trackers and alocalizer for identifying the position and orientation of the tracker,comprising receiving identity data from at least one tracker of thenavigation system, said tracker identity data being unique for eachtracker in the navigation system; receiving position and orientationdata of a tracker interface being attached to a tracker interface of anattachment component; obtaining calibration data defining the positionand orientation of a portion of the instrument relative a trackerinterface of the attachment component; and translating the position andorientation data of the tracker interface into position and orientationdata of the instrument using said identity data and said calibrationdata.
 14. A computer program product stored on a computer usable medium,comprising: computer readable program means for causing a computer tocarry out the method of claim 13 when executed.